An example of the social “get out the vote” message shown to more than 60 million Facebook users on Election Day in November 2010. Other users in the study saw an informational message – identical in all respects – except for photographs of friends.

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An example of the social “get out the vote” message shown to more than 60 million Facebook users on Election Day in November 2010. Other users in the study saw an informational message – identical in all respects – except for photographs of friends.

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About 340,000 more people turned out to the polls on Election Day in 2010 because of a single message to 60 million Facebook users, according to a study led by the University of California San Diego.

The authors of the study, to be published Thursday in the science journal Nature, said it validates the power of peer pressure in helping get out the vote and demonstrates that social networks can shape important “real-world” behavior.

Dr. James Fowler, UC San Diego political science professor and the study’s lead author, said it suggests social influence may be the best way to increase voter turnout. Behaviors changed not only because people were directly affected, but also because their friends (and friends of friends) were affected, Fowler said.

“This really I think is the first study to show that online social networks can effect these real-world behaviors at a scale that’s potentially important,” he said.

“If we want to make the world a better place on a massive scale, we should focus not just on changing a person’s behavior, but also on utilizing the network to influence that person’s friends,” he added.

Future plans call for studying what kind of messages are most effective and what sort of people are most influential in spreading the message through the network.

Titled “A 61-million-person experiment in social influence and political mobilization,” it is perhaps the largest such trial ever conducted. It comes amid an explosion of social media. Facebook, for example, is nearing 1 billion active users.

In the study, researchers randomly assigned nonpartisan get-out-the-vote messages to 61 million Facebook users at the top of their “newsfeeds” on Nov. 2, 2010.

Messages carried a reminder that “Today is Election Day,” a clickable “I voted” button, a link to nearby polling places, a counter displaying how many users already reported voting, and up to six profile pictures of users’ own Facebook friends who reported voting.

Some 600,000 people were randomly assigned a modified “informational message” that was identical to the other except for the pictures of their friends. Another 600,000 served as the control group and received no message about the election.

Users who received the social message were more likely to research their polling place and to click on the “I voted” button.

Researchers said they determined people who voted that might not have without the message by comparing the online behavior with voting records in 13 states. They relied on group-level matching to preserve privacy while also allowing statistical analysis at the individual level. That includes matching users to registration lists by name and date of birth. Four percent of those who said they voted hadn’t cast ballots.

Political candidates, from President Barack Obama and Republican nominee Mitt Romney, to those running for city and school board posts, have increasingly turned to the web and social networks to broadcast their messages and communicate with potential voters. At the same time candidates also are using applications and other virtual venues to tailor their messages to smaller but no less influential clusters of voters and donors.

While recent evidence suggests it may be possible to harness online social networks to influence web behavior, Fowler said, no one to date has shown that online social networks could influence important offline behaviors.

The study finds that close friends who are likely to have a face-to-face relationship accounted for nearly all of the social influence in the network even though they make up just 7 percent of all online relationships. While the average Facebook user has about 150 friends, only the 10 closest mattered for the spread of real-world voting.

Voter turnout, or lack thereof, has long been the focus of academic research. For the congressional election in November 2010, the turnout was 38 percent of the voting-age population, according to the U.S. Census Bureau.

Cameron Marlow, Facebook’s head of data science and a co-author of the study, said outside researchers were provided access to company data and operated under the same guidelines as employees. Work was done on large-scale hardware that does not reveal individual identities, he said.

As for the company’s interest, Marlow said it is committed to being involved in the democratic process and helping to turn out voters. He would not say whether the company had any similar plans for the Nov. 6 election.

The study shows users who received a message, but not the photos of their friends, voted at the same rates as those who saw no message at all.

Conservative estimates show the overall effort directly boosted turnout by 60,000 people. The influence didn’t stop there, according to the study. The social network yielded an additional four voters for every one directly mobilized voter. An estimated 280,000 more friends showed up to the polls.

“All totaled, a single message on Election Day on Facebook got 340,000 people to vote in real elections,” Fowler said, noting only 20 percent of that was due to the direct effect of the message.

There were no differences in effects among self-described liberals and conservatives. Marlow said it was important to consider that not all users provide information about their partisan leanings on their profiles, presenting challenges in representing the precise impact on the outcome at the polls.

The study was supported in part by the James S. McDonnell Foundation, the University of Notre Dame and the John Templeton Foundation as part of the Science of Generosity Initiative.

Morley Winograd, senior fellow at the Center on Communication Leadership and Policy at the USC Annenberg School for Communication and Journalism, said the study confirms the importance of social connections in working to increase voter turnout.

“Contacting voters blindly doesn’t do much at all because there is no social component,” said Winograd, co-author of “Millennial Momentum: How a New Generation is Remaking America” and former chairman of the Michigan Democratic Party. “What is fascinating here is that social media could be used to make that social connection.”

Political scientists have experimented with a number of get out the vote messages and have found their effect in general elections ranges from about 1 percent to 10 percent depending on the type of contact. Knocking on doors is most effective and electronic communication is the least. The Facebook study appears to have registered on the lower end of that scale.

Some of what’s known about what drives people to the polls comes from a quartet of academic researchers commissioned by the governor of Texas. The series of randomized experiments, conducted in the heat of his 2006 campaign, are detailed in the book “Rick Perry and His Eggheads: Inside the Brainiest Political Operation in America.”

Winograd, who was not involved in the studies, suggested it would be wise for supporters of Obama and Romney to put out their own “I voted” messages to friends.